Process for making tall oil



grade is not essential. .simple and highly economical method for furvsodium carbonate and'sodium sulfide.

Patented July 17, 1951 UNITED STATES PATENT OFFICE signor to Kirby Chemical Company, Inc.,

Severn, N. 0., a corporation of North Carolina No Drawing. Application September 3, 1948,

' Serial No. 47,744

' 14 Claims. 1

This invention relates toprocess for making tall oil. More particularly, this invention relates to a process for making high quality crude tall oil from the black liquor soap skimmings obtained in the sulfate pulping process and to a process for further refining the tall oil obtained.

The crude tall oils, hitherto initially obtained from the black liquor soap skimmings by the usual acidification methods possess such disadvantageous characteristics as to be generally useless unless subjected to costly refining procedures. I have discovered that by acidifying under certain carefully regulated conditions, I obtain a high quality crude tall oil which not only is superior to the crude tall oils hitherto produced, but closely approximates in its characteristics many refined tall oils presently available, so that it may be directly employed without further refining for many uses where a highly purified I have also devised a ther purifying the high grade crude oil initially produced by my new process, which results in a high yield of tall oil of improved character' istics.

It is an object of this invention to provide/a new and improved process for making crude oil from black liquor soap skimmings which is of such improved characteristics as to render it usable for many purposes without further refinmg.

Another object is to provide a new and improved process for refining the crude tall 011 obtained by my method, which is simple, economical and produces a refined talloil that may be employed industrially for uses which require tall oils of the highest quality.

Other objects and advantages will become apparent from the following description of .the processes for carrying out my invention.

The crude tall oil soap skimmings which are obtained in conventional manner from the black liquor produced in the sulfate pulping processyis first washed with the cooking liquor employed. in the sulfate digestion process, namely,'white liquor, which is a mixture of sodium hydroxide,

Thisipreliminary washing with white liquor .is advantageous inasmuch as it removes some of the .un-

desirable organic impurities with a consequent saving in the quantity of sulfuric acid consumed in the subsequent acidulation step, but is not essential. The white liquor after being used as a wash for the soap skimmings may be directly employed in the pulping process so that its use as a washing medium is very economical.

The tall oil soap skimmings may then be subjected to a second wash with a solution of sodiumsulfate or sodium chloride, preferably having -a concentration of about 10 to 14 percent. Like the preliminary wash with white liquor, this extraction with sodium sulfate solution is "not essential but is helpful in reducing the amount of acid required in the acidification procedure, by removing such impurities as free alkali from the soap. The washings should be removed as completely as possible in any desired manner, as, for example, by centrifuging.

The tall oil soap skimmings are then acidified with a dilute aqueous solution of sulfuric acid having a concentration withina range of 10'to 40 percent'by weight. I have found that concentrations above 40 percent result in undesirable sulfonation side reactions and charring. Concentrations below 10 percent not only slow up the reaction rate unduly, but .require'the application of .higher'temperatures than arerdesirabla-as will be hereinafter described. Within the available range of 10 to 40 percent I have found that concentrations of acid rof about 3,0-percentare prefaerable.

The quantity of .acid added must be sufficiently in excess of the theoretical amount required, so

that after completion .of the reaction a ,-minimum of "10 per cent sulfuric acid remains un reacted. The reaction is considered to ,be substantially complete when the tall oil obtained .has an acid number of at least 170. I have obtained good results with :an excess of acid up .to 20 percent. The actual quantity of sulfuric acid needed will, of course, be determined by such .factors as the amount of sulfate soap treated, the composition of the particular soap which will vary somewhat according to the Generally .15 percent by weight of 66 degrees Baum sulfuric acid diluted to the .de- :siredconcentration, pbasedon the weight of the soap, will be sufficient to provide the necessary excessof acid. Hitherto, it has been considered "deleterious to-employ any appreciable excess 'of acid. However, I have found that an excess such as aforedescribed is essential in order to obtain tall oil having the desired high acid number. Under the conditions of my process the presence of this excess acid does not result in any unde- 5 sirable side reactions or by-products.

The aqueous solution of sulfuric acid is introduced into a tank or chamber containing the soap skimmings either unwashed or washed as hereinbefore described, and forms a layer at the by the injection of steam into the bottom por- 5 tion of the tank under a pressure of 50 to 100 pounds. I have found it particularly advantageous to start with a steam pressure of about 50 to 60 pounds and then to increase the pressure to about 80 pounds when boiling begins,

When steam having pressures within the range of 50 to 100 pounds is used, it is substantially entirely absorbed by the acid layer until the boilin point is reached so that there is substantially no bubbling of steam to the surface. In consequence, the acid layer is evenly heated throughout and there is relatively no circulation :of material within the tank until the acid solution comes to a boil, at which time the rapid ebullition of the acid solution ensures thorough, $0

rapid and uniform admixture of the acid and soap. By thus preventing the formation of cir- .culating currents through the material before .rapid ebullition starts, undesirable charring and sulfonation reactions are avoided. When circulifi lating currents are formed prior to boiling, small 4 quantities of the soap are carried through the acid layer and are thereby subjected to relatively large quantities of acid for an extended interval .and,the consequent local action not only frees, i:0 thetall oil acids from the soap, but presents .yconditions conducive to undesirable side reactions. Circulating currents which result in undesirable local action, are produced when the .higher steam pressures generally employed him-.

erto are used with consequent bubbling of steam to the surface prior to boiling, or when the heat- -ing means results in uneven heating, as for example, when heat is externally applied. 1 lower temperature of the lower pressure steam I1 employ as compared with the high pressure, high I temperature steam hitherto considered necessary,

The

further reduces the undesirable sulfonation and At this stage of the The reaction mixture is then allowed to The tall oil product which floats to the top is drained off and is ready for use as such,

or may be further refined as hereinafter de-: 5

scribed.

The tall oil obtained as a result of the foregoing procedure is free of many of the deleterious properties which has made crude tall oil hitherto obtained generally useless unless subjected to exten-T 70 sive refining procedures.

To distinguish the tall oil which I obtain by my improved process without further refining from the crude tall oil hitherto obtained by present methods, I shall here- 4 premium crude tall oil may be employed for many purposes which have hitherto required refined tall oil.

The following table sets out the characteristics of the premium crude oil obtained by my process:

Table 1 Color read on Gardner varnish scale 16-18 Sulfonated products Substantially none Unsaponifiables 5-7 percent Moisture l-1 percent Acid number 170-175 Viscosity on Gardner sca1e S The premium crude tall oil is light in color, having a reading on the Gardner varnish scale of 16-18, Whereas all crude tall oils hitherto obtained are too dark to read on this scale at all. This light color is stable, furthermore, since the tall oil is substantially free from sulfonated byproducts which usually cause darkening after a short period of time. Premium .crude tall oil has been stored for more than eight months with no appreciable darkening.

The premium crude tall oil is of relatively low viscosity as compared with the highly viscous ordinary crude oils, so that it flows readily. Furthermore, the viscosity shows no substantial increase even after prolonged storage. Whereas ordinary crude oils contain as high as 20 percent of unsaponifiable materials, premium crude tall oil contains only 5 to 7 percent. It has a mild odor and is low in moisture content.

Not only does my new process produce a stable tall oil of superior quality, but it is economical, inasmuch as it gives yields of about to 57 percent based on the weight of the soap skimmings. Such yields are considerably higher than those hitherto obtained.

Although my premium crude tall oil meets the specifications for a refined tall oil with respect to many of its characteristics, as for example,

stability, viscosity, substantial freedom from sulfonated impurities and moisture content, its

' uses.

I have devised a novel process for refining the premium crude tall oil so as to produce a very light tall oil of improved characteristics. My process has the further advantages of being simple and highly economical both as to materials employed, and yield, and of giving a uniform product.

The premium crude oil is dissolved in an inert organic solvent, such as petroleum naphtha or petroleum ether, preferably in the ratio of about 1 to 2 parts of solvent to 1 part of oil. The solution is centrifuged, or otherwise clarified to remove the undissolved matter which includes any remainin ligneous materials. The resulting sludge is so minor in amount, comprising at most about 2 percent by weight of the oil, that it can be readily disposed of, as by burning.

The clear solution is then treated with an acid or heat activated bleaching earth. The use of bleaching earth in the refining of tall oil is well known. However, I have discovered that by adding a very minor quantity of concentrated sulfuric acid, concentrated phosphoric acid, or a boron trifluoride complex, such as the acetic acid and ether complexes with the acid or heat activated bleaching earth, that I can reduce the I amount of bleaching earth re uired b 60- to after employ the term premium crude. My .75 q y '80 percent. The sulfuric acid, phosphoric acidor borontrifiuoride complex apparently functions as an activating catalyst for the bleaching earth. In practice, about 1 part of bleaching earth to parts of crude oil is sufficient when about 1 to about 2 percent of the activating catalyst is included in the mixture, based on the weight of the oil. Somewhat higher percentages of the activating catalyst may be employed, but in general about 1 to 2 percent is sufficient for optimum results. Where sulfuric acid is used as the catalyst, care should be exercised to avoid concentrations which are so high as to cause undesirable sulf onation or charring reactions. About 10 percent by weight of bleaching earth based on the weight of tall oil generally gives optimum results. Larger quantities may be employed without adverse ef feet on the oil, but the use of such larger quantitles for the most part will merely add to the cost with no substantial increase in emcacy. In the absence of the activating catalyst about 3 to 5 times more bleaching earth is required to accomplish the same result. Any suitable acid or heat activated bleaching earth may be used, as for example, bleachin earths known to the industry as Special Filtrol, Super Filtrol, Floraid and others.

The premium crude tall oil, bleaching earth and catalyst mixture is agitated at ordinary temperatures for about to 30 minutes, after which the bleaching earth is filtered off. No appreciable sludge is formed and filtration is simple and rapid. The filtrate is given a single wash with water, which is then drained off and the solvent removed, as by distillation. The recovered solvent may then be re-employed.

The resulting refined tall oil product is of uniform and improved quality, as evidenced from the following characteristics set out in Table II.

Table II Color on Gardner varnish scale 9-11 Moisture Less than 1 percent Sulfonated products Substantially none Viscosity on Gardner scale U Unsaponifiables 4-6 percent Acid number 170-175 The odor is mild and there is no darkening of color or increase in viscosity during storage.

The tall oil is especially adapted for industrial uses which require a highly refined product. Because of the absence of sulfonated by-products, it is particularly useful. in the manufacture of synthetic esters for use in drying oils.

The refined tall oil is obtained in yields of 92 to 95 percent, based on the weight of crude oil. This high yield may be attributable to several factors. Substantially no sludge is formed with no consequent loss by entrainment. Because of the relatively small amount of bleaching earth used there is little adsorption loss. Even when sulfuric acid is used as the activating catalyst, no sulfonated products are formed, because of the low concentration of acid and the low temperature. In the usual refining procedures which employ relatively high percentages of sulfuric acid, as the refining agent, sulfonated products are formed which are difficult to remove completely and reduce the yield.

The absence of any appreciable sludge formation, eliminates the usual disposal problem. Since the refining process is carried out at ordinary temperatures, there is little loss of solvent due to volatilization. The minor quantities of acid catalyst used makes expensive acidv resistant linings unnecessary.

6 The following example is illustrative of the invention; but does not limit its scope in any way:

Example 10,000 pounds of sulfate soap skimmings were washedwith 1,000 pounds of white liquor. The liquor was allowed to settle and then drained off. The soap was then subjected to a second wash with 1,000 pounds of 10 percent sodium sulfate solution and then centrifuged to remove as much of the wash as possible. A 30 percent solution of sulfuric acid containing 1,500 pounds of 66 degree Baum sulfuric acid was then added to the washed soap skimmings. The acid solution formed a layer at the bottom of the tank. Steam under a pressure of about 50 pounds was injected into the acid layer until the solution. began to boil. The pressure of the injected steam was raised to pounds and. boiling was continued: until the tall oil produced had an. acid number of 170. The reaction mixture was allowed to settle and the tall oil which formed a layer at the top was drained off. About 5700 pounds of a light color crude tall oil having the characteristics outlined in Table I above. were obtained.

The tall oil thus obtained was dissolved in 1400 gallons of petroleum naphtha. The resulting solution was centrifuged to remove undissolved matter. 570 pounds of activated bleach ing earth was added to the clarified solution. While the bleaching earth was being added, concentrated sulfuric acid. in amount approximately 1 percent of the weight of the tall oil was also added. The mixture was a itated for about 30 minutes, after which time the bleaching earth was filtered off. The solution was Washed once with 200 gallons of water, which was then drained off. The solvent was then removed by distillation. Approximately 5,250 pounds of a light yellow, refined tall oil having the characteristics outlined in Table II above, were obtained.

. Similar results are obtained when the activating catalyst for the activated bleaching earth is either phosphoric acid or a boron trifiuoride complex, such as the acetic acid-complex or the ether complex.

Although this invention has been described with reference to illustrating embodiments thereof, it will. be apparent to those skilled in the art that the principles of this invention may be embodied in other forms, but within the scope of the appended claims.

Having thus described my invention, I claim:

1. A process for producing tall 011 from sulfate soap skimmings com-prising heating an aqueous solution comprising. about 10 to 40 percent sulfuric acid, said sulfuric acid being present in sufiicient amount to provide at least about 10 percent free excess sulfuric acid after completion of the reaction, preventing any appreciable commingling of the soap skimmings and acid solution until the boiling point of the acid solution is reached, effecting the rapid, intimate commingling of the entire mass of soap with the acid solution by the ebullition of said acid solution, heating until the tall oil is substantially completely freed from the soap, and separating said tall oil from the reaction mixture.

2. A-process for producing tall oil from sulfate soapskirnmings comprising, floating said soap on an aqueous solution comprising. about 10 to 40 percent sulfuric acid, said sulfuric acid being presentv in. sufiicient amount to provide at least about 10 percent free excess sulfuric acid after awnin 7 completion of the reaction, heating said acid solution substantially evenly throughout in such a manner that no substantial commingling of the soap and acid solution occurs until the boiling point of the acid solution is reached, continuing said heating until the tall oil is substantially completely liberated, and then separating said tall oil.

3. A process for producing tall oil from sulfate soap skimmings comprising, floating said soap on an aqueous solution comprising about 10 to 40 percent sulfuric acid, said sulfuric acid being present in suflicient amount to provide at least about 10 percent free excess sulfuric acid after completion of the reaction, applying heat by the direct injection of steam into said acid solution under a pressure such that substantially all of said steam is absorbed by said acid solution said steam serving to evenly heat said solution so that no substantial commingling of the soap and acid solution occurs until the boiling point of the acid solution is reached, continuing said heating until the tall oil is substantially completely liberated, and then separating said tall oil.

4. A process for producing tall oil from sulfate soap skimmings comprising, floating said soap on an aqueous solution comprising about 10 to 40 percent sulfuric acid, said sulfuric acid being present in sufiicient amount to provide at least about 10 percent free excess sulfuric acid after completion of the reaction, applying heat by the direct injection of steam under a pressure of about 50 to 100 pounds into said acid solution,

said steam serving to evenly heat said solution so that no substantial commingling of the soap and acid solution occurs until the boiling point of the acid solution is reached, continuing said heating until the tall oil is substantially completely liberated and then separating said tall oil.

5. A process for producing tall oil from sulfate soap skimmings comprising, floating said soap on an aqueous solution comprising about 10 to percent sulfuric acid, said sulfuric acid being present in sufficient amount to provide-at least about 10 percent free excess sulfuric acid after completion of the reaction, applying heat by the direct injection of steam under a pressure of about to 100 pounds into said acid solution, said steam serving to evenly heat said solution so that no substantial commingling of the soap and acid solution occurs until the boiling point of the acid solution is reached, continuing said heating until the tall oil formed has an acid number of at least about 170, and then separating said tall oil.

6. A process for producing tall oil from sulfate soap skimmings comprising, floating said soap on an aqueous solution comprising about 30% sulfuric acid, said sulfuric acid being present in sufiicient amount to provide at least about 10 percent free excess sulfuric acid after completion of the reaction, applying heat by the direct injection of steam under a pressure of about 50 to 100 pounds into said acid solution, said steam serving to evenly heat said solution so that no substantial commingling of the soap and acid solution occurs until the boiling point of the acid solution is reached, continuing said heating until the tall oil formed has an acid number of at least 170, and then separating said tall oil.

7. A process for producing tall oil from sulfate soap skimmings comprising, floating said soap on an aqueous solution comprising about 30% sulfuric acid, said sulfuric acid being present in suflicient amount to provide at least about 10 ,75

percent free excess sulfuric acid after completion of the reaction, applying heat by the direct injection of steam under a pressure of about 50 to 60 pounds into said acid solution, said steam serving to heat said acid solution substantially evenly throughout in such a manner that no substantial commingling of the soap and acid solution occurs until the boiling point of the acid solution is reached, increasing the pressure of said steam to about pounds and continuing said heating until the tall oil formed has an acid number of at least 170, and then separating said tall oil.

8. A process for producing tall oil from sulfate soap skimmings comprising, Washing said soap with White liquor, removing said White liquor, Washing said soap with an aqueous solution of a salt selected from the group consisting of sodium sulfate and sodium chloride, removing said salt solution, then floating said soap on an aqueous solution comprising about 10 to 40 percent sulfuric acid, said sulfuric acid being present in suflicient amount to provide at least about 10 percent free excess sulfuric acid after completion of the reaction, applying heat by the direct injection of steam under a pressure of about 50 to pounds into said acid solution, said steam serving to evenly heat said solution so that no substantial commingling of the soap and acid solution occurs until the boiling point of the acid solution is reached, continuing said heating until the tall oil is substantially completely liberated, and then separating said tall oil.

9. A process for producing refined tall oil from sulfate soap skimmings as claimed in claim 1, including the further steps of dissolving said tall oil in an inert, organic solvent, separating out undissolved matter, treating the solution with an activated bleaching earth in admixture with a minor quantity of a compound selected from the group consisting of sulfuric acid, phosphoric acid and a boron trifiuoride complex, separating said solution from the solid matter, Washing said solution, and removing said organic solvent.

10. A process for producing refined tall oil from sulfate soap skimmings as claimed in claim 3, including the further steps of dissolving said tall oil in an inert, organic solvent, separating out undissolved matter, treating the solution with an activated bleaching earth, in admixture with a minor quantity of a compound selected from the group consisting of sulfuric acid, phosphoric acid and a boron trifiuoride complex, separating the solution from the solid matter, washing said solution, andv removing said organic solvent.

11. A process for producing refined tall oil from sulfate soap skimmings as claimed in claim 3, including the further steps of dissolving said tall oil in inert, organic solvent in a ratio of one part of tall oil to about one to two parts of solvent, separating out the undissolved matter, treating the resulting solution with an activated bleaching earth in a ratio of at least one part of bleaching earth to about ten parts of tall oil, in admixture with a compound selected from the group consisting of sulfuric acid, phosphoric acid, and a boron-trifiuoride complex, said compound being present in an amount comprising about one to about two percent by weight of the tall oil, separating the solution from the solid matter, washing the solution with water, removing the water and then distilling off the organic solvent.

12 A process for producing refined tall oil from sulfate soap skimmings as claimed in claim 3,

including the further steps of dissolving said tall oil in an inert, organic solvent in a ratio of one part of tall oil to about one to two parts of solvent, separating out the undissolved matter, treating the resulting solution with an activated bleaching earth in a ratio of at least one part of bleaching earth to about ten parts of tall oil, in admixture with a compound selected from the group consisting of sulfuric acid, phosphoric acid, and a boron trifluoride complex, said compound being present in an amount comprising about one and one-half percent by weight of the tall oil, said compound serving to increase the activity of said bleaching earth, separating the solution from the solid matter, Washing the solution with water, removing the water, and then distilling off the organic solvent.

13. A process for producing refined tall oil from sulfate soap skimmings as claimed in claim 4, including the further steps of dissolving said tall oil in inert, organic solvent in a ratio of one part of tall oil to about one to two parts of solvent, separating out the undissolved matter, treating the resulting solution with an activated bleaching earth in a ratio of at least one part of bleaching earth to about ten parts of tall oil, in admixture with a compound selected from the group consisting of sulfuric acid, phosphoric acid, and a boron-trifluoride complex, said compound being present in an amount comprising about one to about two percent by weight of the tall oil, separating the solution from the solid matter, wash= ing the solution with water, removing the water and then distilling off the organic solvent.

14. A process for producing refined tall oil from sulfate soap skimmings as claimed in claim 4, including the further steps of dissolving said tall oil in an inert organic solvent in a ratio of one part of tall oil to about 1 to 2 parts of solvent, separating out the undissolved matter, treating the resulting solution with an activated bleaching earth in a ratio of at least one part of bleaching earth to about 10 parts of tall oil, in admi'x ture with sulfuric acid, said sulfuric acid being present in an amount comprising about 1 to about 2% by Weight of the tall oil, separating the solution from the solid matter, washing the solution with water, removing the water and then distilling on the organic solvent,

RAYMOND W. STEPHENSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,200,468 Cirves May 14, 1940 2,374,975 Borglin May 1, 1945 2,413,009 Taussky Dec. 24, 1946 2,430,029 Pollak et al. Nov. 4, 1947 2,434,699 Huff Jan. 20, 1948 

1. A PROCESS FOR PRODUCING TALL OIL FROM SULFATE SOAP SKIMMINGS COMPRISING HEATING AN AQUEOUS SOLUTION COMPRISING ABOUT 10 TO 40 PERCENT SULFURIC ACID, SAID SULFURIC ACID BEING PRESENT IN SUFFICIENT AMOUNT TO PROVIDE AT LEAST ABOUT 10 PERCENT FREE EXCESS SULFURIC ACID AFTER COMPLETION OF THE REACTION, PREVENTING ANY APPRECIABLE COMMINGLING OF THE SOAP SKIMMINGS AND ACID SOLUTION UNTIL THE BOILING POINT OF THE ACID SOLUTION IS REACHED, EFFECTING THE RAPID, INTIMATE COMMINGLING OF THE ENTIRE MASS OF SOAP WITH THE ACID SOLUTION BY THE EBULLITION OF SAID ACID SOLUTION, HEATING UNTIL THE TALL OIL IS SUBSTANTIALLY COMPLETELY FREED FROM THE SOAP, AND SEPARATING SAID TALL OIL FROM THE REACTION MIXTURE. 